The Diversity of Type Ia Supernovae: Evidence for Systematics?

By S. Benetti, E. Cappellaro, P. Mazzali, Massimo Turatto, G. Altavilla, Filomena Bufano, N. Elias-Rosa, R. Kotak, G. Pignata, M. Salvo and 1 more. 2004

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The photometric and spectroscopic properties of 26 well-observed Type Ia Supernovae (SNe Ia) were analyzed with the aim of exploring SN Ia diversity. The sample includes (Branch) normal SNe, as well as extreme events such as SN 1991T and SN 1991bg, while the truly peculiar SNe Ia, SN 2000cx and SN 2002cx, are not included in our sample. A statistical treatment reveals the existence of three different groups. The first group (FAINT) consists of faint SNe Ia similar to SN 1991bg, with low expansion velocities and rapid evolution of Si II velocity. A second group consists of normal SNe Ia, also with high temporal velocity gradient (HVG), but with brighter mean absolute magnitude ⟨MB⟩ = -19.3 and higher expansion velocities than the FAINT SNe. The third group includes both normal and SN 1991T-like SNe Ia: these SNe populate a narrow strip in the Si II velocity evolution plot, with a low-velocity gradient (LVG), but have absolute magnitudes similar to HVGs. While the FAINT and HVG SNe Ia together seem to define a relation between ℛ(Si II) and Δm15(B), the LVG SNe either do not conform to that relation or define a new, looser one. The ℛ(Si II) premaximum evolution of HVGs is strikingly different from that of LVGs. We discuss the impact of this evidence on the understanding of SN Ia diversity, in terms of explosion mechanisms, degree of ejecta mixing, and ejecta-circumstellar material interaction.

Subfields: Astronomy and Astrophysics, Electrical and Electronic Engineering, Instrumentation

View Paper: https://www.semanticscholar.org/paper/3848b2171e30cc62d38bd2a24c6a72b2d91c4d30

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In Astronomy and Astrophysics

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Citations in the corpus

• Fourteen months of observations of the possible super-Chandrasekhar mass Type Ia Supernova 2009dc (2010, methodology): “Since v has been evaluated at 10 and 40 d past maximum for similar analyses previously (Benetti et al. 2005; Howell et al. 2006), we will use a range of velocities from 7000 km s−1 to 5500 km s−1 for our analysis.”
• Early and late time VLT spectroscopy of SN 2001el - Progenitor constraints for a type Ia supernova (2005, background): “More recently Benetti et al. (2005) divided ‘normal’ SNe Ia into groups showing high (HVG) and low (LVG) temporal velocity gradients for the Si II profile after the maximum light.”
• Hubble Space Telescope spectra of the type Ia supernova SN 2011fe: a tail of low-density, high-velocity material with Z < Z⊙ (2013, background): “As the ejecta expand, the photosphere recedes inside the ejecta following the decreasing density, as witnessed by the decreasing blueshift of the observed spectral lines (e.g. Benetti et al. 2005).”
• IMPROVED DISTANCES TO TYPE Ia SUPERNOVAE WITH TWO SPECTROSCOPIC SUBCLASSES (2009, background): “At a given phase there is a large spread among the absorption blueshifts of their spectral features (e.g., Benetti et al. 2005, hereafter B05), and there are also differences in line strengths.”
• Spectrophotometric time series of SN 2011fe from the Nearby Supernova Factory (2013, methodology): “The velocity gradient of Si λ6355, as defined by Benetti et al. (2005), was computed using a linear least squares fit for −2 < t < +25 d overplotted on Fig.”
• Nearby supernova rates from the Lick Observatory Supernova Search – I. The methods and data base (2010, background): “SNe Ia are grouped into the following subclasses: (a) normal objects (e.g., Branch & Tammann 1992), (b) high expansion velocity objects (Benetti et al. 2005; Wang et al. 2009), (c) SN 1991T-like objects (Filippenko et al. 1992a; Phillips et al. 1992), (d) SN 1991bg-like objects (Filippenko et al.…”
• K-Corrections and Spectral Templates of Type Ia Supernovae (2007, background): “Some of these differences are associated with the variation in light-curve shapes (Nugent et al. 1995; Benetti et al. 2005; Hachinger et al. 2006), while the origins of others remain unknown.”
• Comparative Direct Analysis of Type Ia Supernova Spectra. I. SN 1994D (2005, background): “Pastorello et al. (2007) referred to SN 2004eo as a transitional SN Ia because its properties placed it between the three groups (faint, low velocity gradient, and high velocity gradient) of Benetti et al. (2005).”
• High luminosity, slow ejecta and persistent carbon lines: SN 2009dc challenges thermonuclear explosion scenarios (2010, unknown): “In a hierarchical cluster analysis, Benetti et al. (2005) arranged all SNe Ia in three groups (LVG, HVG and FAINT) based on their post-maximum velocity gradient and their m15(B).”
• Determining the Type, Redshift, and Age of a Supernova Spectrum (2006, background): “This corresponds to a combination of the typical velocity shift in SN Ia absorption features from maximum to ∼ 10 days past maximum, and the spread of these velocities at a given age (∼ 3000 km s−1; see Benetti et al. 2005; Blondin et al. 2006a).”
• Observational Clues to the Progenitors of Type Ia Supernovae (2013, background): “Benetti et al. (2005) have separated SNe Ia into two classes – those with “low velocity gradients” and those with “high velocity gradients” – based on the decrease with time in the velocity of the Si II λ6355 absorptions, v̇Si, with the border at 70 km s −1 d−1.”
• Two populations of progenitors for type ia supernovae (2005, result): “The systematic differences measured in the expansion velocities of the ejecta of SNe Ia occurring in Ellipticals and Spirals (Branch & van den Bergh 1993; Benetti et al. 2005) are indeed fully consistent with our results.”
• THE SPECTROSCOPIC DIVERSITY OF TYPE Ia SUPERNOVAE (2000, methodology): “We thus reproduce the main result of Maeda et al. (2010a), although they base their spectroscopic classification on the velocity gradient of the Si iiλ6355 line defined by Benetti et al. (2005) as opposed to its absorption velocity at maximum (all the HV SN Ia in Fig.”
• SN 2003du: 480 days in the life of a normal type Ia supernova (2007, background): “…et al. 2004, Stehle et al. 2005; SN 2002dj – Pignata et al. 2005; SN 2002er – Pignata et al. 2004, Kotak et al. 2005; SN 2003cg – Elias-Rosa et al. 2006; SN 2004eo – Pastorello et al. 2007a; SN 2005cf – Pastorello et al. 2007b, Garavini et al. 2007; Benetti et al.2005; Mazzali et al. 2005a).”
• Optical and Near-Infrared Observations of the Highly Reddened, Rapidly Expanding Type Ia Supernova SN 2006X in M100 (2007, methodology): “Our collection of nebular-phase spectra of SN 2006X is presented in Figures 18 and 19, together with the spectra of some comparison SNe Ia at similar epochs.”
• The rates of type Ia supernovae - I. Analytical formulations (2005, result): “Some diversities of the observational properties of SNIa have been found in the literature, which support this notion (e.g. Branch 2005, Benetti et al. 2005).”
• An Open Catalog for Supernova Data (2016, background): “…anything from finding commonalities between seemingly different supernova types, to generating mean spectra and exploring spectroscopic diversity (Benetti et al. 2005; Branch et al. 2005, 2006, 2007, 2008, 2009; Wang et al. 2009; Blondin et al. 2012; Folatelli et al. 2013; Maguire et al. 2014;…”
• Spectropolarimetry of Supernovae (2008, background): “Ap., 27, 629 Benetti et al. (2004)Benetti, S. et al. 2004, MNRAS, 348, 261 Benetti et al.(2005)Benetti, S., et al. 2005, Ap.”